Just in case the message that he is evil isn't successfully conveyed by his menacing presence and cold, mechanical breathingby Ne Quis

He choked his fashion co-ordinator waaay back.by X-Wing Jedi

Hides that alderaanian ale belly and that gut from all those greasy nerfburgers....by Gryfft

Lucas to Guy In Charge of Dressing: "Come on, it's the dark side. All the bad guys gotta wear black." "No, George, that's not a good idea. White's in nowadays." "Welll, how about just one? The rest you can put in white suits."by Gryfft

Because Billy Dee Williams "called dibs" on the powder blue cape before he got there.by snowdog83

So he's easier to snipe among all those white stormtroopers...by -anonomous

he was made fun of alot by the kids in the jedi academyby lightningcount

Gray was already taken by EVERYBODY else in the Empireby RyanAdc

He needs something suitable to wear to all the funerals of all the people he kills.by Jake Skywalker

For a reason defined years ago in the Expanded Universe and generally regarded as concrete until Lucas writes the next prequelby Ne Quis

Darth: "Because George told me too..."by Darth Vanilla Shake

He'd be laughed out of the Society of Evil Overlords if he didn't!by Dark Helmet

FOOLS! Do you really believe I need a reason?! The Dark Lord of the Sith needs no reason! You all shall pay for your insolence!(reaches out with the force and asphyxiates the entire TFN staff and all who submitted a reason.)by Darth Vader